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bpf: add skb->tstamp r/w access from tc clsact and cg skb progs 

This could be used to rate limit egress traffic in concert with a qdisc
which supports Earliest Departure Time, such as FQ.

Write access from cg skb progs only with CAP_SYS_ADMIN, since the value
will be used by downstream qdiscs. It might make sense to relax this.

Changes v1 -> v2:
  - allow access from cg skb, write only with CAP_SYS_ADMIN

Signed-off-by: Vlad Dumitrescu <vladum@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Vlad Dumitrescu 2018-11-22 14:39:16 -05:00 committed by Alexei Starovoitov
parent ab85b01434
commit f11216b242
4 changed files with 60 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/uapi/linux/bpf.h
View File

@ -2468,6 +2468,7 @@ struct __sk_buff {
__u32 data_meta;
struct bpf_flow_keys *flow_keys;
__u64 tstamp;
};
struct bpf_tunnel_key {

29
net/core/filter.c
View File

@ -5573,6 +5573,10 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
if (size != sizeof(struct bpf_flow_keys *))
return false;
break;
case bpf_ctx_range(struct __sk_buff, tstamp):
if (size != sizeof(__u64))
return false;
break;
default:
/* Only narrow read access allowed for now. */
if (type == BPF_WRITE) {
@ -5600,6 +5604,7 @@ static bool sk_filter_is_valid_access(int off, int size,
case bpf_ctx_range(struct __sk_buff, data_end):
case bpf_ctx_range(struct __sk_buff, flow_keys):
case bpf_ctx_range_till(struct __sk_buff, family, local_port):
case bpf_ctx_range(struct __sk_buff, tstamp):
return false;
}
@ -5638,6 +5643,10 @@ static bool cg_skb_is_valid_access(int off, int size,
case bpf_ctx_range(struct __sk_buff, priority):
case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):
break;
case bpf_ctx_range(struct __sk_buff, tstamp):
if (!capable(CAP_SYS_ADMIN))
return false;
break;
default:
return false;
}
@ -5665,6 +5674,7 @@ static bool lwt_is_valid_access(int off, int size,
case bpf_ctx_range_till(struct __sk_buff, family, local_port):
case bpf_ctx_range(struct __sk_buff, data_meta):
case bpf_ctx_range(struct __sk_buff, flow_keys):
case bpf_ctx_range(struct __sk_buff, tstamp):
return false;
}
@ -5874,6 +5884,7 @@ static bool tc_cls_act_is_valid_access(int off, int size,
case bpf_ctx_range(struct __sk_buff, priority):
case bpf_ctx_range(struct __sk_buff, tc_classid):
case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):
case bpf_ctx_range(struct __sk_buff, tstamp):
break;
default:
return false;
@ -6093,6 +6104,7 @@ static bool sk_skb_is_valid_access(int off, int size,
case bpf_ctx_range(struct __sk_buff, tc_classid):
case bpf_ctx_range(struct __sk_buff, data_meta):
case bpf_ctx_range(struct __sk_buff, flow_keys):
case bpf_ctx_range(struct __sk_buff, tstamp):
return false;
}
@ -6179,6 +6191,7 @@ static bool flow_dissector_is_valid_access(int off, int size,
case bpf_ctx_range(struct __sk_buff, tc_classid):
case bpf_ctx_range(struct __sk_buff, data_meta):
case bpf_ctx_range_till(struct __sk_buff, family, local_port):
case bpf_ctx_range(struct __sk_buff, tstamp):
return false;
}
@ -6488,6 +6501,22 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
*insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg,
si->src_reg, off);
break;
case offsetof(struct __sk_buff, tstamp):
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, tstamp) != 8);
if (type == BPF_WRITE)
*insn++ = BPF_STX_MEM(BPF_DW,
si->dst_reg, si->src_reg,
bpf_target_off(struct sk_buff,
tstamp, 8,
target_size));
else
*insn++ = BPF_LDX_MEM(BPF_DW,
si->dst_reg, si->src_reg,
bpf_target_off(struct sk_buff,
tstamp, 8,
target_size));
}
return insn - insn_buf;

1
tools/include/uapi/linux/bpf.h
View File

@ -2468,6 +2468,7 @@ struct __sk_buff {
__u32 data_meta;
struct bpf_flow_keys *flow_keys;
__u64 tstamp;
};
struct bpf_tunnel_key {

29
tools/testing/selftests/bpf/test_verifier.c
View File

@ -2446,6 +2446,10 @@ static struct bpf_test tests[] = {
offsetof(struct __sk_buff, tc_index)),
BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,
offsetof(struct __sk_buff, cb[3])),
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1,
offsetof(struct __sk_buff, tstamp)),
BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0,
offsetof(struct __sk_buff, tstamp)),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "",
@ -5297,6 +5301,31 @@ static struct bpf_test tests[] = {
.errstr_unpriv = "R2 leaks addr into helper function",
.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
},
{
"write tstamp from CGROUP_SKB",
.insns = {
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0,
offsetof(struct __sk_buff, tstamp)),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.result_unpriv = REJECT,
.errstr_unpriv = "invalid bpf_context access off=152 size=8",
.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
},
{
"read tstamp from CGROUP_SKB",
.insns = {
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1,
offsetof(struct __sk_buff, tstamp)),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
},
{
"multiple registers share map_lookup_elem result",
.insns = {